The pictures show a plug where the hot leads go through the fire wall. You first need to remove the battery and battery shelf (very easy). There you will find the big rubber plug.

Move the carpet on the passenger side floor back from the upward part of the floor and you will find the panel that is held by three plastic nuts (just don't let them fall into the cavity as you remove them) and the upward part of the floor lifts away to reveal the power amp and associated wiring.

Nip off one of the tips on the big rubber plug and send a 8 gauge wire through and you will find it comes out the other side in the passenger compartment where you can easily use the Painless Wiring fuse panel or make your own like I did.

Be sure to put a circuit breaker between the battery and the wire BEFORE it goes through the fire wall. Even though you have fuses on your devices, you want a breaker to prevent the car catching on fire if the wire going through the firewall should happen to short out.

When you get everything wired and tested, button it all back up and with the battery back in place, you will find you need to clear a warning light that has to do with the steering sensor. You just need to center the steering and then turn the steering wheel all the way left and right twice and the light will clear. The owners manual has it listed for exact details. You may need to set your clock too...

With that, I have switched and unswitched power sources with fuses for all my extra electronic devices. It's really handy since once installed you just go into the floor space to add new devices.